In a travel control device that makes a vehicle travel automatically at a speed set by a driver, the following travel control technique called adaptive auto cruise as been put into practical use: a distance between the own vehicle and a forward vehicle is detected by a sensor, and when the forward vehicle approaches the own vehicle to a certain extent, the speed of the own vehicle is adjusted in accordance with the speed of the forward vehicle. In recent years, a travel control device has also been put into practical use that performs not only output adjustment of a power train but also brake control, having a function that stops the own vehicle when the forward vehicle is decelerated or stopped.
Since the above-mentioned typical travel control device controls the travel speed of the own vehicle based on a distance and a speed relative to the nearest forward vehicle, it is readily affected by acceleration and deceleration of the nearest forward vehicle, as compared to a case where an experienced driver determines states of a plurality of forward vehicles to thus adjust the speed of the own vehicle, so that there are some cases to cause rapid acceleration and deceleration. Therefore, a follow-up travel control device of Patent Document 1 discloses that calculates a relative positional relationship to not only the nearest forward vehicle but also a plurality of vehicles to thus control the own vehicle, whereby a follow-up travel considering movements the plurality of vehicles can be achieved.
In addition, in order to support a driving for improving fuel economy when a vehicle is stopped in the case where the signal is red at a signalized intersection, a driving support device of Patent Document 2 discloses a configuration which obtains information of signals and vehicle information existing near a stop line via communication from an infrastructure (hereinafter abbreviated to infra), predicts a position in which the own vehicle will stop, to thus carry out the driving for improving fuel economy.
Likewise, a driving support device of Patent Document 3 discloses the following configuration: from signal information and the length of a line of vehicles stopping at an intersection, the timing when the line of the stopped vehicles starts at the time of changing to a green signal is predicted to thus provide a driver with a speed that the own vehicle can pass through the intersection without stop.